import arcpy
import os
input = arcpy.GetParameterAsText(0)
name = os.path.basename(input).rstrip(os.path.splitext(input)[1])
extension = os.path.splitext(input)[1].lstrip(".")

def CheckExtension(extension):
  if extension == 'shp':
    arcpy.SetParameterAsText(1, "true")
    arcpy.SetParameterAsText(2, "false")
  elif extension == 'gpx':
    arcpy.SetParameterAsText(2, "true")
    arcpy.SetParameterAsText(1, "false")

CheckExtension(extension)